Numerical study on impact and freezing characteristics of supercooled droplets on micro-scale rectangular groove-textured superhydrophobic surfaces

In this paper, a numerical model is established to investigate the impacting-freezing behavior of supercooled droplets on grooved superhydrophobic surfaces. The effects of temperature conditions (droplet supercooling degree 5 ∼ 15 °C and cold surface temperature −25 ∼ −5 °C) and groove geometric parameters are systematically studied, with particular emphasis on the evolution of the post-impact modes, heat transfer characteristics, and mass freezing rates. The results show that increasing the supercooling degree and decreasing the cold surface temperature significantly enhance the heat exchange between the droplet and the cold surface, and promote the formation of an initial ice layer at the droplet bottom, thereby increasing the occurrence of the freezing-induced adhesion mode. Specifically, as the surface temperature decreases from −5 °C to −25 °C, the total heat transfer increases by nearly 6 times. The groove depth determines the penetration and capillary-driven retraction of liquid, which in turn affects the surface energy accumulation before rebound. The groove width also affects the droplet penetration behavior, and wider grooves inhibit the spreading of the droplet. These mechanisms jointly lead to a non-monotonic relationship between geometric parameters and post-impact modes, highlighting the competition between ice-phase propagation and kinetic energy release. Furthermore, at high Weber numbers, a composite mode may occur in which the droplet bottom freezes while the upper portion rebounds. This study reveals the fundamental mechanisms of the microstructural parameters on the droplet impacting-freezing behavior, providing a theoretical basis for the design of anti-frosting surface structures.